The present invention relates generally to security systems and, more particularly, to a security system utilizing a magnetic code sensing mechanism for actuating the system. The system of the invention may be utilized with alarm systems with electrically actuated lock mechanisms in order to emit an electrical signal which will either trigger an alarm or unlock the lock mechanism depending upon the code sensed by the precoded sensor which receives the coded magnetic key. The magnetic key of the invention is of the type containing a plurality of magnets formed in the arrangement of a locking or unlocking code. In the operation of devices of the types with which the invention relates, when the appropriate key having the magnetic devices thereon arranged in the predetermined order is inserted into the sensing device, a desired operative mode will be effected in the security system.
Magnetic switch devices of the type to which the invention relates have been proposed, for example, in U.S. Pat. Application Ser. No. 963,275. In magnetic switch devices of this type, the magnets of the magnetic key are arranged in code positions in the form of a grid or pattern which may be optionally arranged, with a magnetic field sensor being provided in a reading unit for each magnet position of the grid. The magnetic field sensors are connected to a comparator which delivers a switch signal when the magnetic field sensors sense a code on the magnetic key which coincides with a code stored in an adjustable code storage unit which is connected with the magnetic comparator. The switch signal of the comparator may be used for unlocking an electrically actuated lock which may be a component part of a central locking system, for example, of the type utilized in motor vehicles. However, the switch signal may also be utilized for triggering an alarm system when the code of the magnetic key sensed by the magnetic field sensors does not coincide with the code which has been stored in the code storage unit.
The locking code stored in the storage unit may always be manually caused to coincide with the code of the magnetic key. However, this property, which is a desirable property in itself, may result in disadvantages. For example, the storage unit could be reprogrammed to another locking code for the purposes of effecting a theft or perhaps merely due to carelessness. In the case of a theft, the motor vehicle which is tampered with in this manner may, of course, be eventually stolen without triggering the alarm system which is provided for the security of the vehicle. However, either in the case of a deliberate reprogramming for the purpose of a theft or inadvertent reprogramming, the magnetic switch lock will no longer be actuated by means of the magnetic key which is intended to appropriately operate the security system. When the magnetic switch lock is used for the central locking system of a motor vehicle, this may have the result that the operator of the motor vehicle may unintentionally lock himself out of the vehicle so that he can no longer gain access to the vehicle because of the inadvertently changed unlocking code.
Thus, the present invention is directed to providing a magnetic security system of the type described wherein the danger of unintentional or unauthorized reprogramming of the locking code is eliminated.